Within seconds of arriving at the North Korean border, a US Army soldier leaps onto the tour bus and starts barking orders.

"No drugs," he says, glowering at the group of mainly American tourists through his dark glasses. "No alcohol. No weapons of any kind, not even penknives.

"And do not, under any circumstances, attempt to communicate with the North Korean soldiers you are about to see."

He marches up and down the bus, checking passports and crossing names off a list, before spinning around to face a sea of tourists' faces.

"Another thing," he adds, "and this is not a joke - are any of you considering defecting to North Korea?"

When no one replies in the affirmative, the group is marched in single file into the Demilitiarised Zone (DMZ), a twisting snake of barbed wire fences, watchtowers and minefields that runs across the entire Korean peninsula.

Visitors using binoculars look at the North Korean village of Gaepung-Gun at the Odusan Unification Observatory near the Demilitarized Zone (DMZ)Credit:
SeongJoon Cho/Bloomberg